(a) Field of the Invention
The present invention relates to a semiconductor device and a method for fabricating a contact of the semiconductor device, in particular, to a semiconductor device having a contact for electrically coupling metal wires formed on different layers and/or an electrodes of the semiconductor device and the metal wire, and a method for fabricating the contact.
(b) Description of the Related Art
Typically, a semiconductor device having MOS transistor, as a field effect transistor (FET), includes a source, drain, and gate electrodes.
The method for fabricating the semiconductor device will be described hereinafter.
Firstly, a gate insulating film and gate electrode are formed on a semiconductor substrate and then a spacer is formed on the side wall of the gate followed by forming source/drain regions. After the above structured MOS transistors are formed, an interlayer insulation film is formed on the entire surface of the semiconductor substrate, and then the interlayer insulation film is planarized using a Chemical Mechanical Polishing (CMP) process.
Next, the interlayer insulation film is etched using a contact mask so as to produce contact holes exposing the source/drain regions, and then a barrier metal film is formed by depositing Ti/TiN film on the upper surface of the interlayer insulation film and the inner wall of the contact hole. Here, the barrier metal film can be formed using Physical Vapor Deposition (PVD) process or Chemical Vapor Deposition (CVD) process.
Sequentially, the contact hole is filled by depositing a conductive layer on the interlayer insulation film such as tungsten film. Here, the tungsten film can be formed using CVD process. Then, the conductive layer and the barrier metal film is polished using the CMP or blanket etch back process until the surface of the interlayer insulation film is exposed so as to form the contact which electrically connects to the source/drain regions below.
However, in the conventional contact fabrication method, it is not easy to form a contact with a high aspect ratio lager than 10:1. This is due to the seam effect in which the inlet of the contact hole is closed before the contact hole is filled out. The seam effect is caused by the step coverage limit of the tungsten film filled in the contact hole. The void formed by the seam effect degrades the electrical characteristic and productivity of the semiconductor
Accordingly, there has been researches and developments for forming the contact with void. The U.S. Pat. Nos. 5,747,379 and 6,025,269 disclose the methods for fabricating the void free contacts.